Magnetic Domain Structures of High Permeability Alloys

The magnetic domain wall images in permalloy and 5% Mo-permalloy with high magnetic permeabilities were observed by means of Lorentz microscopy. The specimens were of the form of thin films prepared by electrolysis of bulk materials. Correlating these observations with the initial permeabilities, it was found that, as the initial permeabilities become high, the magnetic domain walls change their appearances from straight lines to curved lines and finally they vanish in part. In a local part about 20µ in diameter of the specimen with permeability at 0.001 Oe, µ 0.001 =120,000, typical circularly magnetized domain pattern has been observed for the first time in a monograin state. The energy calculation for this configulation with circular magnetization was performed. Comparing this result with that for a uniformly magnetized domain, the existence of the circularly closed magnetic domain in low effective anisotropy–high permeability–magnetic materials is justified.